Hajisafarali M., Aaltonen S., Pulkkinen K., Taskinen J.
Decline of freshwater mussels (Unionida) is a global phenomenon, threatening biodiversity and the essential ecosystem services that mussels provide. Freshwater mussels can clear the water by filtering suspended particles, such as phytoplankton, but they can also remove bacteria from the water and therefore decrease the risk of infections in aquatic organisms. Here, we studied if the common freshwater bivalve Anodonta anatina (duck mussel) can remove Flavobacterium columnare from water. This bacterium is the causative agent of columnaris disease in fish, which causes serious problems in aquaculture. Mussels removed bacteria from the water in two experiments performed, so that after 96-h monitoring, the concentration in mussel treatments was only 0.3–0.5 times that of the controls. Mussel behavior (shell openness, foot position, and movement) was not affected by the presence of bacteria or algae. Biodeposition formation was higher with algal diet than with bacterial diet, and lowest in clean water. The intestines of A. anatina that were offered bacteria, harbored F. columnare, suggesting that mussels ingested the bacteria. From the ecosystem services angle, present result supports the view that freshwater mussels can have an influence on bacteria, and suggests that freshwater mussels have a potential to mitigate problems caused by aquaculture pathogens as well as to play a role in water quality management.